In the past, it had been found desirable to build motors using semi-closed slots 10 (see FIG. 1) in stator laminations 12 to improve motor performance. This necessarily resulted in increased difficulty in manufacturing motors, particularly in inserting windings into the stator slots because of the reduced accessibility of the slot with a semi-closed entry. One solution was to provide for fully open slots, with greater ease of coil insertion which permitted form wound coils 14 (see FIG. 2) but resulted in a reduction in motor performance when used with top wedges 18 without magnetic properties.
Various efforts have been undertaken to provide magnetic slot wedges with wire or iron powder or fillings imbedded in a carrier. Each of these approaches has, however, failed to approach the performance obtainable with a semi-closed slot design.
More recently, efforts have been undertaken to provide magnetic wedges formed of laminated magnetic material with the wedge laminations directly abutting stator laminations in the slot as exemplified by U.S. Pat. No. 4,425,521 for a magnetic slot wedge with low average permeability and high mechanical strength. Such an approach, however, suffers from the disability that stator laminations may be short circuited at the stator-wedge interface when the wedge laminations are offset from the stator laminations as may readily occur in practice. Such short circuits at the stator-wedge interface will permit eddy currents with the consequent energy loss and interference with the magnetic fields in this region.
In addition to the above, prior art structures have required handling of the individual laminations to get them into alignment to form a wedge, resulting in relatively high manufacturing expense.
The present invention overcomes the shortcomings of the prior art by providing for a magnetic slot wedge having insulation of predetermined thickness between the wedge laminations and the stator laminations. Additionally, means are provided for aligning wedge laminations in a simple and efficient manner, thus reducing manufacturing costs.